1. Field of the Invention
The invention relates to a restraining system for a driver of a vehicle.
2. The Prior Art
Various restraining systems for drivers of fork-lift trucks are known from the FTL-Research Report of the Gerhardt-Mercator Universitxc3xa4t Gesamthochschule Duisburg. These restraining systems hold the driver within the cabin in the event the floor conveyor vehicle tilts over. This feature is important for preventing the driver from falling under the vehicle while the vehicle is rolling over, which would lead to very serious injuries. These restraining systems protect the driver and do not inhibit movement of the driver when he is getting into or out of the vehicle or during operation. The published report proposes a rollover bar that can be swiveled in an approximately horizontal restraining position into a vertical release position on the left driver""s side. However, this rollover bar does not have a locking mechanism, therefore, it can move into the release position at any time, i.e. also while the vehicle is rolling over, and therefore offers inadequate protection for the driver. Another embodiment shown in the published document contains a rollover bar that can be swivelled into the release position by a hydraulic cylinder or a lifting magnet. The rollover bar is actively connected with a contact switch attached to the seat and swivels the rollover bar into the restraining position as soon as the driver sits on the driver""s seat. For swiveling the rollover bar into the release position, the driver needs to actuate a separate switch. This rollover bar system does provide adequate safety for the driver. However, it cannot be used in conjunction with small electrically operated fork-lift trucks because of the high power consumption of the lifting magnet. Since small, electrically operated fork-lift trucks have a very high center of gravity when lifting loads because of their low weight, and because they are typically equipped with an open cabin, a high demand exists for an effective restraining system for the driver.
An object of the present invention is to provide a restraining system that offers effective protection for the driver in the event the vehicle rolls over. Another object of the present invention is to provide a system that can be employed in conjunction with small vehicles as well.
These and other objects are accomplished by providing a restraining system containing at least one safety rollover bar mounted next to the seat of the driver. The safety rollover bar is capable of swiveling around a shaft between a vertical release position and a horizontal restraining position. When the safety rollover bar is in the release position, the driver can climb into and out of the vehicle without any obstruction. This is particularly important when there are confined space conditions, such as in warehouse facilities. Furthermore, the driver is not hindered by the restraining system. Therefore, the restraining system would be accepted by the drivers and would not be dismantled by the operator. When in the restraining position, the protective rollover bar is hip level and extends along at least half of the seat to provide adequate protection of the driver when the vehicle tilts over. To install the restraining system in small electric fork-lift trucks, the shaft is actively connected with the electric motor via a transmission. As compared to a lifting magnet, the electric motor of this system has particularly low power consumption and uses a small amount of energy from the on-board network of the vehicle. If need be, an AC-DC converter or a voltage bypass for adaptation to the on-board network can be provided. The range of the vehicle, which is limited by the electric charge stored in the batteries, would not be significantly reduced. This advantage is very important for the restraining system to be accepted. The motor is actively connected to the shaft via the transmission so that the electric motor can transmit the required torque to the shaft. The transmission reduces the rotational motion of the driving shaft of the electric motor so that the electric motor can be economically operated within the range of the desired number of revolutions. The swiveling motions of the shaft and the safety rollover bar occur at a low speed to avoid excessive forces of acceleration.
In another preferred embodiment, the shaft is maintained in the retaining position by the force of the electric motor so that an additional locking device is not needed. However, this would cause the electric motor to continually draw electrical current from the on-board network of the vehicle, which would reduce the range of the vehicle accordingly. Alternatively, the transmission between the shaft and the electric motor can be a self-inhibiting transmission, for example a worm gearing. However, a self-inhibiting transmission has a relatively poor efficiency rate that would lead to increased energy consumption as well. To avoid this drawback, it is preferred that the shaft is locked in the restraining position. This is accomplished by providing a cam disk to support the shaft. The cam disk is driven by the electric motor. A locking pin engages a breakthrough in the cam disk in the form of a divided circle, whereby the locking pin is axially displaced by the cam disk. The shaft is driven by the electric motor via a dead gear, which permits the cam disk to retract the locking pin before the shaft is swiveled. This movement is advantageous for locking the shaft in the restraining position.
In another preferred embodiment, a simple and effective locking device is provided by the cam disk forming at least one support surface for the locking pin. When the pin is moved by the electric motor it scans the support surface. The support surface has an inclined gradient allowing the locking pin to be axially displaced between a locking position and a release position as it moves along the cam disk. This axial movement of the locking pin is advantageous for locking the shaft.
In the locked position, the locking pin cooperates with a locking cam. The locking cam is stationarily supported so that any turning of the shaft while in the locking position is avoided. The effectiveness of the restraining system is dependent upon the working order of the on-board electrical network of the vehicle or on the electric motor.
The cam disk can also be provided with support surfaces for the locking pin. The surfaces are directed against each other, so that the pin can be forcibly adjusted in the axial direction. However, it is preferred that the locking pin be spring-loaded against the cam disk. In this case, one support surface suffices and the support surface is scanned by the locking pin.
A switch or key device can be provided for actuating the electric motor. Therefore, the shaft can be driven into the release position at any time. In the event the on-board electrical network or of the electric motor fails, shifting the shaft into the release position would no longer be possible. To make it possible for the driver to exit the vehicle, the locking pin is connected to a hand lever. The manual lever shifts the locking pin into the release position without actuating the electric motor. Since a separate hand lever has to be actuated for releasing the shaft, the safety of the retaining system while driving the vehicle is not impaired.
To obtain the simplest structure for the retaining system, the shaft contains an oblong hole into which a pin for transmitting the torque from the electric motor to the shaft is placed.
To control the retaining system and at the same time maintain high safety for the driver, it is advantageous if the safety rollover bar is used as the locking device. For this purpose, the safety rollover bar is swiveled into the retaining position about a vertical axis between a locking position and a releasing position. Therefore, an additional device is not required to release the shaft. The shaft has at least one support surface that operates with the safety rollover bar when in its locked position. The support surface prevents the safety rollover bar from swiveling outwards. In addition, the shaft can be turned into the release position by the electric motor or automatically with a spring, or by the effect of gravity of the safety rollover bar.
To enhance the safety benefits of the rollover bar, it is preferred that at least two support surfaces are provided on the shaft. One of the support surfaces is located on the face side and the other on the side facing the shaft, thereby achieving the safest possible locking effect.
To safely retain the rollover bar in the locking position when it is not actuated, it is spring-loaded in the direction of the restraining position.
In the release position, the safety rollover bar is swiveled toward the driver to prevent the shaft from being unlocked while the vehicle is rolling over. In this case, the driver presses against the safety rollover bar providing an additional load in the direction of the locking position.
To ensure that the safety rollover bar is maintained in the restraining position, the shaft is engaged by at least one spring to force the shaft in the direction of swivel. If necessary, the spring can be supported by the electric motor.
For achieving the best possible acceptance of the safety rollover bar by the driver, the shaft is supported on the driver""s seat. Therefore, the shaft and the safety rollover bar are simultaneously adjusted with the driver""s seat so that the relative position between the two is always preserved. Furthermore, when the driver""s seat is adjusted in a low position, the driver is prevented from slipping out from under the safety rollover bar. As an alternative, the shaft can be supported on the frame of the vehicle, which simplifies the installation of the entire restraining system.
In addition, the position of the shaft can be adjustable. Therefore, each driver can adjust the safety rollover bar to his individual needs. This is accomplished by providing telescope-like elements for extending the height of the shaft so that the lateral spacing of the bar from the seat can be adjusted in accordance with the needs of the driver as well.
Furthermore, to prevent the shaft from turning beyond the release or restraining position, the shaft contains a final stop device. These stop devices are preferably formed by pins that cooperate with the locking cam.
To achieve safe locking of the shaft in the restraining position, at least one pin engages a bore in a metal holding sheet. The metal holding sheet is supported in a stationary manner and bent in the form of a xe2x80x9cZxe2x80x9d to lessen the impact of the safety rollover bar when shifted into the retaining position.
To make sure that the safety rollover bar is always in the retaining position while the vehicle is being operated, the shaft is may contain a sensor. When the vehicle is ready for operation, the sensor automatically turns the shaft into the restraining position. The sensor device could be a contact on the driver""s seat that registers the driver on the seat. As an alternative, the sensor could monitor the position of the selector switch for selecting the driving direction, the manual brake, the pedal whip or the steering joy stick. The sensor could also monitor the speed of the vehicle or the position of the lifting gear of the vehicle. The sensor assures that while the vehicle is operating, the safety rollover bar is in the restraining position to protect the driver.
Finally, the shaft is provided with a locking pin for use when the motor hood is open. This would prevent swiveling of the safety rollover bar when service or maintenance work is performed on the vehicle and also substantially simplifies the maintenance work.